1. Field of the Invention
The present invention relates to a bonding member including two or more of different kinds of members joined together. More particularly, the present invention relates to an electrostatic chuck which can be suitably used in a semiconductor manufacturing device.
2. Description of the Related Art
Conventionally, a brazing material has been used in a method for bonding a ceramic member and a metal member. However, during the cooling operation after bonding is performed at a high temperature, thermal stress occurs due to the difference in the coefficient of thermal expansion between the different kinds of members, or between the members and the brazing material used to join these different kinds of members. Accordingly, peeling or cracks occur in the vicinity of the bonding interface when one of the members is fragile. Thus, the desired bonding strength and airtightness may not be obtained. Products in which such problems as described above arise in a manufacturing process thereof have to be disposed of as defective products. Thus, the problems described above contribute to increasing product costs of these bonding members. Moreover, if there is a heat cycle when the members are used, the problems described above arise after the members are used for a fixed period of time. Accordingly, the problems also lower the reliability of the product.
In consideration of the present situation described above, a bonding method has been studied which maintains moderate bonding strength between different kinds of members, without lowering the bonding strength due to thermal stress in the vicinity of the bonding interface during a cooling operation after bonding is performed at a high temperature, and without generating cracks in a cooling operation for a member that is vulnerable to the thermal stress. For example, there is disclosed a method for obtaining a bonding layer by using brazing filler metal as a base and adding particles to the brazing filler metal which lower thermal stress (for example, see Japanese Patent No. 3315919). Moreover, there is also disclosed a method for joining different kinds of members together when a width of a gap existing between wall surfaces of the different kinds of members in a fitting structure portion is narrow (for example, see Japanese Patent Laid-Open No. 2001-10873). Furthermore, there is also disclosed a bonding adhesive composition which includes a brazing filler metal and a mixture of at least two kinds of particles having different wettability from the brazing filler metal (for example, see Japanese Patent Laid-Open No. 2001-122673).
Moreover, as a product which requires bonding of a ceramic member and a metal member, for example, an electrostatic chuck used in a semiconductor process or the like is enumerated. In this electrostatic chuck, the ceramic member and the metal member are joined together in a portion of a substrate, which has built-in electrodes and is made of ceramics or the like, and a terminal, which supplies power to the built-in electrodes, and is made of gold-plated molybdenum or the like.
As described above, various methods for joining a ceramic member and a metal member have been known which do not cause a lowering of bonding strength nor generate cracks during a cooling operation for a member that is vulnerable to thermal stress. However, even by using the methods described above, residual stress is likely to be concentrated in a corner portion when different kinds of members are joined by adopting a structure in which a concave portion is fitted to a convex portion. Therefore, cracks sometimes occur.